I have a massive migraine right now but I am going to try to answer your questions. In the past I used to heat my urine to about 110 before securing it. After much practice I don't even heat mine that much or use a thermometer, I can tell what is 100-105 degrees. Heating it to 110 to 115 isn't going to damage the sample.

You are completely making this too difficult on yourself trying to get to the center in 5 minutes. You cannot imagine how much heat your body gives off because you are used to your own body heat. Heat it to 100 degrees (the temp strip is on the bottle) and stick it on you. If it is still in between 90-100 degrees 45 minutes later chances are it will stay at that temp indefinitely. It isn't nuclear fusion. Just practice. Take the bottle and make sure it gets good skin exposure then check it at 30 minutes, 1 hour, 2 hours. It isn't that hard and you will be surprised how well you body keeps it warm. Your body is like an oven you just are used to it and don't realize how much heat it is giving off. You are just nervous and over thinking this. Don't speed from your house to the site and cause a wreck. You will be fine.

Now off to deal with my headache but I'll check back later. Quit making it hard on yourself. Sorry for spelling/grammer errors.